• Structural Engineering and Mechanics
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• v.85 no.4
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• pp.433-443
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• 2023

The current paper discusses the dynamic and stability responses of cross-ply composite laminated plates by employing a refined quasi-3D trigonometric shear deformation theory. The proposed theory takes into consideration shear deformation and thickness stretching by a trigonometric variation of in-plane and transverse displacements through the plate thickness and assures the vanished shear stresses conditions on the upper and lower surfaces of the plate. The strong point of the new formulation is that the displacements field contains only 4 unknowns, which is less than the other shear deformation theories. In addition, the present model considers the thickness extension effects (ε_z≠0). The presence of the Winkler-Pasternak elastic base is included in the mathematical formulation. The Hamilton's principle is utilized in order to derive the four differentials' equations of motion, which are solved via Navier's technique of simply supported structures. The accuracy of the present 3-D theory is demonstrated by comparing fundamental frequencies and critical buckling loads numerical results with those provided using other models available in the open literature.

• The Korean Journal of Community Living Science
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• v.27 no.spc
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• pp.703-714
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• 2016

Dwelling environments that can help elderly farmers to live more safely, independently, and conveniently are becoming more and more important. Many rural houses are built without any particular architectural or energy-related criteria, so most of them have poor insulation. The construction technology used is also not precise, which increases the loads for heating and cooling. Therefore, rural houses need to be improved. Also, there is more and more need for plans to realize eco-friendly dwellings, so the principle of nature-oriented plans related to the direction, insulation, or landscaping of a house is being emphasized. Insulation is one of the most effective ways to save energy for heating and cooling. This preliminary study to improve the insulation of rural houses examined three regions in South Korea: the central region, the southern region, and the Jeju Island. A field investigation was conducted on a total of 18 houses, including six from each town in the selected regions. The information was used to figure out the current status of rural houses and the characteristics of the buildings. The main living spaces are the living room for the central region and the main room in the southern region and Jeju Island. The southern regions are plane shapes surrounded by rooms, and all ventilation is accomplished by windows. The studied houses were mostly masonry structures with slate rooftops. Additions and improvements included room expansions and bathroom interior installations.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.2
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• pp.147-157
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• 2011

A RANS(Reynolds averaged Navier-Stokes) based numerical method is developed for the evaluation of ship resistance and self-propulsion performances. In the usability aspect of CFD for the hull form design, the field grid around practical hull forms is generated by solving a grid Poisson equation based on the hull surface grid generated from station offsets and centerline profile. A body force technique is introduced to model the effects of the propeller in which the propeller loads are obtained from potential flow analysis using an unsteady lifting surface method. The free surface is captured by using a two-phase level-set method and the realizable $k-{\varepsilon}$ model is used for turbulence closure. The hull attitude in vertical plane, i.e., trim and sinkage, is calculated by using a quasi-steady method and then considered in the computation by translating and rotating the grid system according to the values. For the validation of the proposed method, the numerical results of resistance tests for KCS, KLNG, and KVLCC1 and of self-propulsion test for KCS are compared with experimental data.

• Structural Engineering and Mechanics
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• v.44 no.6
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• pp.775-799
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• 2012

This work approaches the structural performance of masonry arches that have a small ratio between number of vossoirs and span length. The aim of this research is to compare and validate three different methods of analysis (funicular limit analysis F.L.A., kinematic limit analysis K.L.A. and plane stress Finite Element Analysis F.E.A.) with an experimental campaign. 18 failure tests with arches of different shapes and boundary conditions have been performed. The basic failure mechanism was the formation of enough hinges in the geometry. Nevertheless, in few cases, sliding between vossoirs also played a relevant influence. Moreover, few arches didn't reach the collapse. The FLA and KLA didn't find a solution close to the experimental values for some of the tests. The low number of vossoirs and joints become a drawback for an agreement between kinematic mechanism, equilibrium of forces and geometry constraints. FLA finds a lower bound whereas KLA finds an upper bound of the ultimate load of the arch. FEA is the most reliable and robust method and it can reproduce most of the mechanism and ultimate loads. However, special care is required in the definition of boundary conditions for FEA analysis. Scientific justification of the more suitability of numerical methods in front of classic methods at calculating arches with a few vossoirs is the main original contribution of the paper.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.131-138
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• 2015

In this paper, the modified live-load and designed formula are studied according to the fact the highway bridge design specifications are recently revised. The two examples for composite steel plates and PSC girder bridges are studied. The envelope is analyzed with the finite element models and lateral load distribution method applying the existing highway bridge specification(2010), the newly revised highway bridge specification(2015) and AASHTO LRFD. In case of composite steel plates, length changes between spans are studied, and in case of PSC girder. changes of the number of cross-beams and spans, and span-lengths, are analyzed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.6
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• pp.77-83
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• 2019

Upon installing a seismic isolation device on a nuclear power plant, the device takes on the suppression of seismic loads. This is expected to bring about a larger displacement than what is seen prior to the installation of the seismic isolation device. Depending on the displacement change, the seismic risk for some equipment can increase. Particularly in case of the piping system, which is used for connecting the structure isolated from seismic events with common structures, the seismic risk is expected to rise significantly. In this study, the limit state of the steel pipe tee, which is a vulnerability part of the nuclear power plant piping system, was defined as leakage, and an in-plane cyclic loading test was conducted. As it is difficult to measure the moment and rotation of the steel pipe tee using the conventional sensors, an image signal was used. This study proposed a leakage line and low-cycle fatigue curves using the relationship between the moment and the rotation of a 3-inch steel pipe tee.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.7
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• pp.575-582
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• 2018

The spaceborne cooler is applied to cool down of the focal plane of the infrared detector of the observation satellite. However, this cooler induces unnecessary micro-jitter which can degrade the image quality of the high-resolution observation satellite. In this study, we proposed a multi-layered blade type vibration isolator to attenuate micro-vibration generated from a spaceborne cooler, while assuring structural safety of the cooler under severe launch loads without an additional launch-lock device. The blade of the isolator is formed with multi-layers in order to obtain durability against fatigue failure and an adhesive is applied between each layers for granting high damping capability under launch vibration environment. In this study, the basic characteristics of the isolator were measured using the free-vibration test. The effectiveness of the isolator design was demonstrated by launch vibration test at qualification level.

• Steel and Composite Structures
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• v.34 no.5
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• pp.643-655
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• 2020

In the present work, the buckling behavior of a single-layered graphene sheet (SLGS) embedded in visco-Pasternak's medium is studied using nonlocal four-unknown integral model. This model has a displacement field with integral terms which includes the effect of transverse shear deformation without using shear correction factors. The visco-Pasternak's medium is introduced by considering the damping effect to the classical foundation model which modeled by the linear Winkler's coefficient and Pasternak's (shear) foundation coefficient. The SLGS under consideration is subjected to compressive in- plane edge loads per unit length. The influences of many parameters such as nonlocal parameter, geometric ratio, the visco-Pasternak's coefficients, damping parameter, and mode numbers on the buckling response of the SLGSs are studied and discussed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.112-119
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• 2021

The failure mode of piping systems due to seismic loads is the low-cycle fatigue failure with ratcheting, and it was found that the element in which nonlinear behavior is concentrated and damage occurs is the elbow. In this study, to quantitatively express the failure criteria for a pipe elbow of SCH40 3-inch carbon steel under low-cycle fatigue, the limit state was defined as leakage, and the in-plane cyclic loading test was conducted. For the carbon steel pipe elbow, which is the vulnerable part to seismic load of piping systems, the damage index was represented using the moment-deformation angle relationship, and it was compared and analyzed with the damage index calculated using the force-displacement relationship. An attempt was made to quantitatively express the limit state of the carbon steel pipe elbow involving leakage using the damage index, which was based on the dissipated energy caused by repeated external forces.

• Journal of the Korean Geotechnical Society
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• v.22 no.9
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• pp.23-36
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• 2006

This study presents the development of a new closed-form analytical solution for the ultimate bearing capacity of an embedded wall in a granular mass. The closed-form analytical solution consists of upper and lower bound solutions (UB and LB). The calculated values from these bound solutions were compared with the author's two-dimensional laboratory wall model loading test and finite element analysis in the plastic region. The comparison showed that ultimate bearing loads from both the model test and finite element analysis are located between UB and LB. In particular, the ultimate bearing load from LB showed good agreement with the ultimate bearing load values from both the model test and finite element analysis. However, the calculated value from the conventional empirical form subjected to plane-strain conditions was shown to be much smaller than the LB.